Roberto Mancini fears Manchester City's title challenge could collapse this month if he is not allowed to buy to strengthen his squad.

Mancini will now be without Yaya and Kolo Toure for up to six weeks, with the brothers having been ordered to report on Saturday for African Cup of Nations duty with Ivory Coast.

That means the pair will miss Sunday's potentially epic FA Cup third round tie with local rivals Manchester United, for which Gareth Barry suspended.

Mancini is more concerned at the impact the Toures' enforced absence - in particular that of Yaya - could have on City's quest for the title, with his side currently holding a three-point lead over United.

The imminent introduction of UEFA's new Financial Fair Play rules means he will have to sell before he can buy, despite the club being bankrolled by Sheikh Mansour's billions.

The club hope to offload Carlos Tevez, Nedum Onuoha and Wayne Bridge in this month's window, but Mancini said he must be allowed to strengthen regardless to ensure he keeps City's title charge on track.

"I think in January - and I said this two months ago - we could have a big problem," he said Mancini. "We play four important games, big games, without Yaya.

"We could take in one player, but it depends. If we have strikers injured, then we will need to buy another.

"At the moment, I have only one striker because Edin Dzeko has a problem in his knee. So I have one striker and two midfielders.

"This month, we are losing two players in Yaya and Kolo. If we lose another, then we will need [to bring in] more players.

"Yaya is an important player for us. Kolo is different, because we have eight defenders and, if we are lucky and don't have injuries, I don't think we'll have a big problem there.

"But in midfield we have a big problem - for Sunday we have only two players there."

Mancini admitted he has been told by City's football administrator Brian Marwood, who is in overall charge of transfer policy, that he must sell to buy.

"I think it's better that we sell first," agreed Mancini. "Maybe then we can then take in other players.

"But this is the problem. If we don't have the players, then it's [going to be] tough for us.

"We are not Manchester United or Chelsea. They have won trophies for many years, but for us it's different.

"This could be our first championship for many years and we need to do everything we can to win it."

With Barry suspended, Mancini's only available central midfielders are James Milner and Nigel De Jong, as Owen Hargreaves is not fit to face his former club.

And with Dzeko and Mario Balotelli both injured and exiled striker Carlos Tevez still AWOL in his native Argentina, Mancini's only fit striker for Sunday is top scorer Sergio Aguero.

On the prospect of Tevez finding a new club, the City boss added: "I hope for him that he can close [a deal] with a team this week, because it's now three months since he played, and I think it's correct that he should begin to play."